/* Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.activiti.engine.delegate;

import org.activiti.bpmn.model.*;
import org.activiti.engine.ActivitiException;
import org.activiti.engine.impl.context.Context;
import org.activiti.engine.impl.delegate.ActivityBehavior;
import org.activiti.engine.impl.el.ExpressionManager;
import org.activiti.engine.impl.el.FixedValue;
import org.activiti.engine.impl.persistence.entity.ExecutionEntity;
import org.activiti.engine.impl.util.ProcessDefinitionUtil;
import org.apache.commons.lang3.StringUtils;

import java.util.ArrayList;
import java.util.List;
import java.util.Map;

/**
 * Class that provides helper operations for use in the {@link JavaDelegate},
 * {@link ActivityBehavior}, {@link ExecutionListener} and {@link TaskListener}
 * interfaces.
 *

 */
public class DelegateHelper {

  /**
   * To be used in an {@link ActivityBehavior} or {@link JavaDelegate}: leaves
   * according to the default BPMN 2.0 rules: all sequenceflow with a condition
   * that evaluates to true are followed.
   */
  public static void leaveDelegate(DelegateExecution delegateExecution) {
    Context.getAgenda().planTakeOutgoingSequenceFlowsOperation((ExecutionEntity) delegateExecution, true);
  }

  /**
   * To be used in an {@link ActivityBehavior} or {@link JavaDelegate}: leaves
   * the current activity via one specific sequenceflow.
   */
  public static void leaveDelegate(DelegateExecution delegateExecution, String sequenceFlowId) {
    String processDefinitionId = delegateExecution.getProcessDefinitionId();
    org.activiti.bpmn.model.Process process = ProcessDefinitionUtil.getProcess(processDefinitionId);
    FlowElement flowElement = process.getFlowElement(sequenceFlowId);
    if (flowElement instanceof SequenceFlow) {
      delegateExecution.setCurrentFlowElement(flowElement);
      Context.getAgenda().planTakeOutgoingSequenceFlowsOperation((ExecutionEntity) delegateExecution, false);
    } else {
      throw new ActivitiException(sequenceFlowId + " does not match a sequence flow");
    }
  }

  /**
   * Returns the {@link BpmnModel} matching the process definition bpmn model
   * for the process definition of the passed {@link DelegateExecution}.
   */
  public static BpmnModel getBpmnModel(DelegateExecution execution) {
    if (execution == null) {
      throw new ActivitiException("Null execution passed");
    }
    return ProcessDefinitionUtil.getBpmnModel(execution.getProcessDefinitionId());
  }

  /**
   * Returns the current {@link FlowElement} where the {@link DelegateExecution} is currently at.
   */
  public static FlowElement getFlowElement(DelegateExecution execution) {
    BpmnModel bpmnModel = getBpmnModel(execution);
    FlowElement flowElement = bpmnModel.getFlowElement(execution.getCurrentActivityId());
    if (flowElement == null) {
      throw new ActivitiException("Could not find a FlowElement for activityId " + execution.getCurrentActivityId());
    }
    return flowElement;
  }

  /**
   * Returns whether or not the provided execution is being use for executing an {@link ExecutionListener}.
   */
  public static boolean isExecutingExecutionListener(DelegateExecution execution) {
    return execution.getCurrentActivitiListener() != null;
  }

  /**
   * Returns for the activityId of the passed {@link DelegateExecution} the
   * {@link Map} of {@link ExtensionElement} instances. These represent the
   * extension elements defined in the BPMN 2.0 XML as part of that particular
   * activity.
   *
   * If the execution is currently being used for executing an
   * {@link ExecutionListener}, the extension elements of the listener will be
   * used. Use the {@link #getFlowElementExtensionElements(DelegateExecution)}
   * or {@link #getListenerExtensionElements(DelegateExecution)} instead to
   * specifically get the extension elements of either the flow element or the
   * listener.
   */
  public static Map<String, List<ExtensionElement>> getExtensionElements(DelegateExecution execution) {
    if (isExecutingExecutionListener(execution)) {
      return getListenerExtensionElements(execution);
    } else {
      return getFlowElementExtensionElements(execution);
    }
  }

  public static Map<String, List<ExtensionElement>> getFlowElementExtensionElements(DelegateExecution execution) {
    return getFlowElement(execution).getExtensionElements();
  }

  public static Map<String, List<ExtensionElement>> getListenerExtensionElements(DelegateExecution execution) {
    return execution.getCurrentActivitiListener().getExtensionElements();
  }

  /**
   * Returns the list of field extensions, represented as instances of
   * {@link FieldExtension}, for the current activity of the passed
   * {@link DelegateExecution}.
   *
   * If the execution is currently being used for executing an
   * {@link ExecutionListener}, the fields of the listener will be returned. Use
   * {@link #getFlowElementFields(DelegateExecution)} or
   * {@link #getListenerFields(DelegateExecution)} if needing the flow element
   * of listener fields specifically.
   */
  public static List<FieldExtension> getFields(DelegateExecution execution) {
    if (isExecutingExecutionListener(execution)) {
      return getListenerFields(execution);
    } else {
      return getFlowElementFields(execution);
    }
  }

  public static List<FieldExtension> getFlowElementFields(DelegateExecution execution) {
    FlowElement flowElement = getFlowElement(execution);
    if (flowElement instanceof TaskWithFieldExtensions) {
      return ((TaskWithFieldExtensions) flowElement).getFieldExtensions();
    }
    return new ArrayList<FieldExtension>();
  }

  public static List<FieldExtension> getListenerFields(DelegateExecution execution) {
    return execution.getCurrentActivitiListener().getFieldExtensions();
  }

  /**
   * Returns the {@link FieldExtension} matching the provided 'fieldName' which
   * is defined for the current activity of the provided
   * {@link DelegateExecution}.
   *
   * Returns null if no such {@link FieldExtension} can be found.
   *
   * If the execution is currently being used for executing an
   * {@link ExecutionListener}, the field of the listener will be returned. Use
   * {@link #getFlowElementField(DelegateExecution, String)} or
   * {@link #getListenerField(DelegateExecution, String)} for specifically
   * getting the field from either the flow element or the listener.
   */
  public static FieldExtension getField(DelegateExecution execution, String fieldName) {
    if (isExecutingExecutionListener(execution)) {
      return getListenerField(execution, fieldName);
    } else {
      return getFlowElementField(execution, fieldName);
    }
  }

  public static FieldExtension getFlowElementField(DelegateExecution execution, String fieldName) {
    List<FieldExtension> fieldExtensions = getFlowElementFields(execution);
    if (fieldExtensions == null || fieldExtensions.size() == 0) {
      return null;
    }
    for (FieldExtension fieldExtension : fieldExtensions) {
      if (fieldExtension.getFieldName() != null && fieldExtension.getFieldName().equals(fieldName)) {
        return fieldExtension;
      }
    }
    return null;
  }

  public static FieldExtension getListenerField(DelegateExecution execution, String fieldName) {
    List<FieldExtension> fieldExtensions = getListenerFields(execution);
    if (fieldExtensions == null || fieldExtensions.size() == 0) {
      return null;
    }
    for (FieldExtension fieldExtension : fieldExtensions) {
      if (fieldExtension.getFieldName() != null && fieldExtension.getFieldName().equals(fieldName)) {
        return fieldExtension;
      }
    }
    return null;
  }

  /**
   * Creates an {@link Expression} for the {@link FieldExtension}.
   */
  public static Expression createExpressionForField(FieldExtension fieldExtension) {
    if (StringUtils.isNotEmpty(fieldExtension.getExpression())) {
      ExpressionManager expressionManager = Context.getProcessEngineConfiguration().getExpressionManager();
      return expressionManager.createExpression(fieldExtension.getExpression());
    } else {
      return new FixedValue(fieldExtension.getStringValue());
    }
  }

  /**
   * Returns the {@link Expression} for the field defined for the current
   * activity of the provided {@link DelegateExecution}.
   *
   * Returns null if no such field was found in the process definition xml.
   *
   * If the execution is currently being used for executing an
   * {@link ExecutionListener}, it will return the field expression for the
   * listener. Use
   * {@link #getFlowElementFieldExpression(DelegateExecution, String)} or
   * {@link #getListenerFieldExpression(DelegateExecution, String)} for
   * specifically getting the flow element or listener field expression.
   */
  public static Expression getFieldExpression(DelegateExecution execution, String fieldName) {
    if (isExecutingExecutionListener(execution)) {
      return getListenerFieldExpression(execution, fieldName);
    } else {
      return getFlowElementFieldExpression(execution, fieldName);
    }
  }

  /**
   * Similar to {@link #getFieldExpression(DelegateExecution, String)}, but for use within a {@link TaskListener}.
   */
  public static Expression getFieldExpression(DelegateTask task, String fieldName) {
    if (task.getCurrentActivitiListener() != null) {
      List<FieldExtension> fieldExtensions = task.getCurrentActivitiListener().getFieldExtensions();
      if (fieldExtensions != null && fieldExtensions.size() > 0) {
        for (FieldExtension fieldExtension : fieldExtensions) {
          if (fieldName.equals(fieldExtension.getFieldName())) {
            return createExpressionForField(fieldExtension);
          }
        }
      }
    }
    return null;
  }

  public static Expression getFlowElementFieldExpression(DelegateExecution execution, String fieldName) {
    FieldExtension fieldExtension = getFlowElementField(execution, fieldName);
    if (fieldExtension != null) {
      return createExpressionForField(fieldExtension);
    }
    return null;
  }

 public static Expression getListenerFieldExpression(DelegateExecution execution, String fieldName) {
   FieldExtension fieldExtension = getListenerField(execution, fieldName);
   if (fieldExtension != null) {
     return createExpressionForField(fieldExtension);
   }
   return null;
  }

}
